As the 3G/4G wireless communication system requires high linearity and high efficiency performance on power amplifier modules, the higher power back-off designs on the front stage, or driver stage improve linearity to drive the final stage amplifier. This higher power back-off mode will operate the MMIC (Monolithic Microwave Integrated Circuit) gain block amplifier at P1 dB-10 dB or provide a more powerful back-off point on the front stage's nominal operation point in a 3G/4G wireless communication system. Traditionally, after system CFR (Crest factor reduction) functions, the waveform PAR (Peak-to-Average Power ratio) will reach between 6 dB to 8 dB PAR and acquires more linear margins for the front stage's back-off at this linear operation region by the MMIC gain block amplifier's AM-AM (Amplitude Modulation-Amplitude Modulation) response properties.
This RF (Radio Frequency) front stage's P1 dB (1 dB compression point) back-off mode can drive an efficient linearity with a higher back-off. However, this may also cause a disadvantage by increasing the margins of the MMIC amplifier's output power capability. As such, the front stage amplifier will have the power capability to output more averaged power within the 6 to 8 dB PAR waveforms. It is also possible to over-drive the final stage amplifier, and damage the final stage amplifier by outputting too much power in many abnormal operations, or system loop fails. In such a situation, the loop either fails, produces incorrect operations, or creates a mismatch on the DPD (Digital Pre-Distortion) feedback loop, or a divergent DPD by non-predistortion amplifier characteristics. It consistently over-drives the amplifier quickly before the amplifier, or system, detects the error and shuts down. This over-drive takes only a period between nanoseconds and microseconds, and damages the final stage amplifier.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.